I don't think it can ever be all or nothing...and it doesn't have to be.
Millions do all or nothing. I don't consider myself "vegan". I'm attacking this from a pure health perspective rather than "for the animals". The byproduct of eating for health is surprisingly pro-animal.
If we didn't eat so much meat, the cows wouldn't be born, so you can likely state eating less meat isn't good for the animals. We wouldn't need near as many and the feed and ground could be used for other things.
But, if you do it 50%, you get 50% of the benefit. People can gauge if 50 or 70% are enough to miss out on the future heart disease and type 2 diabetes and high blood pressure and high cholesterol. 90% probably does keep you out of the woods.
Most people I know have meat, dairy, cheese, eggs (or a mix of all of them) with 90% of meals and not the opposite.
It isn't a meal without a chunk of meat with melted cheese on it in my extended family. Veggies are eaten with butter and/or melted cheese.
We have our usual distribution of breast cancer, prostate cancer, stroke, heart attack, cholesterol that matches the diet. I can only affect myself and my immediate family a little.
It has been a fascinating journey. My mom asks when I'll go back to "regular eating" quite often. Her cholesterol is 300 on medication. It is rough out there.